installing EasyBuild with eb fails when it is using a python version different that the system python one

[migueldiascosta]

seen in #9149, fails during the sanity check

edit: actual failure in sanity check looks like

Sanity check failed: no (non-empty) directory found at 'lib/python3.7/site-packages' in /tmp/software/EasyBuild/4.1.0"

[boegel]

This is a workaround for the problem when trying to install EasyBuild-4.1.0.eb with EB_PYTHON=python3, on a system where /usr/bin/python is the default Python (2.7).

diff --git a/easybuild/easyconfigs/e/EasyBuild/EasyBuild-4.1.0.eb b/easybuild/easyconfigs/e/EasyBuild/EasyBuild-4.1.0.eb
index 65b2ca298a..ad29c55181 100644
--- a/easybuild/easyconfigs/e/EasyBuild/EasyBuild-4.1.0.eb
+++ b/easybuild/easyconfigs/e/EasyBuild/EasyBuild-4.1.0.eb
@@ -41,4 +41,7 @@ sanity_check_paths = {
     'dirs': ['lib/python%s/site-packages' % local_pyshortver],
 }
 
+req_py_majver = 3
+modextravars = {'EB_PYTHON': '/usr/bin/python3'}
+
 moduleclass = 'tools'

The issue is related to the fact that the pick_python_cmd function in PythonPackage blatently ignores the Python being used to run eb with (sys.executable),

[boegel]

Just for future reference, using eb --install-latest-eb-release currently fails if EB_PYTHON=pyhton3 is used for example, while the default system python is Python 2.7, with:

== FAILED: Installation ended unsuccessfully (build directory: /tmp/EasyBuild/4.1.0/dummy-dummy): build failed (first 300 chars):
Sanity check failed: no (non-empty) directory found at 'lib/python3.6/site-packages' in /software/EasyBuild/4.1.0 (took 43 sec)

because:

[09:38:06] {skitty} vsc40023@node3112:~ $ ls /software/EasyBuild/4.1.0
bin  easybuild  etc  lib  lib64
[09:52:38] {skitty} vsc40023@node3112:~ $ ls /software/EasyBuild/4.1.0/lib/
python2.7
[09:52:42] {skitty} vsc40023@node3112:~ $ ls /software/EasyBuild/4.1.0/lib/python2.7/
site-packages
[09:52:44] {skitty} vsc40023@node3112:~ $ ls /software/EasyBuild/4.1.0/lib/python2.7/site-packages/
easybuild  easybuild_easyblocks-4.1.0-py2.7.egg-info  easybuild_easyconfigs-4.1.0-py2.7.egg-info  easybuild_framework-4.1.0-py2.7.egg-info  test

So basically the default system Python is used when installing EasyBuild, rather than the Python used to run eb.

The fix is probably to:

• (first) consider sys.executable in pick_python_cmd
• (always?) set $EB_PYTHON in the module generated for EasyBuild to make sure the Python used at runtime is the same as the one that was used during the installation

cc @jshelley

[boegel]

fixed by the changes in easybuilders/easybuild-easyblocks#1907 + easybuilders/easybuild-easyblocks#1908

[boegel]

fixed now in develop since both PRs are merged, so closing...